1. Technical Field of the Invention
The present invention relates to an insulating resin composition for a multilayer printed-wiring board where conductor layer(s) and insulating layer(s) are alternately laminated one insulating layer after another conductor layer, more particularly to an insulating resin composition which is to be used to form insulating layer(s) of such multilayer printed-wiring board, the resulting insulating layer(s) from which have excellent adhesive properties to the conductor layer(s), high heat resistance and high insulation reliability.
2. Prior Art
In recent years, in accordance with the progress of the reduction and high performance of electronic appliances, the development of printed-wiring board having a high density and a multilayer structure has rapidly proceeded. However, in accordance with the conventional production process in which such multilayer structure is formed by performing the laminating press of a circuit board having a circuit formed, a prepreg and a copper foil, and the connection between the layers is done by a through-hole, the degree of freedom of the circuit design is decreased due to the formation of the through-hole and it becomes difficult to achieve high density. Furthermore, it is required to perform plating the inside of the through-hole, and therefore, the thickness of the conductor becomes large, which is, in turn, disadvantageous for the fine pattern formation.
As a method for solving such problems, recently, attention is being attracted to a manufacturing technique for multilayer printed-wiring boards in a build-up mode, in which an organic insulating layer is laminated on the conductor layer of the circuit board, then followed by laminating conductor layers and organic insulating layers alternately one organic insulating after another conductor layer. For example, in Japanese Patent Application Laid-Open (Kokai) Nos. 7-304931 and 7-304933, there are disclosed methods for producing a multilayer printed-wiring board, according to which an epoxy resin composition is applied onto the circuit board on which a circuit has been formed, and subjected to heat curing, and then, an unevenly roughened surface is formed with a rough surface-forming agent (i.e., surface-roughening agent), and a conductor layer is formed on this roughened surface by plating. Further, in Japanese Patent Application Laid-Open (Kokai) No. 8-64960, there is disclosed a method for producing a multilayer printed-wiring board, according to which a primer adhesive is applied and provisionally dried, a film-form additive adhesive is then laminated thereon, followed by subjecting to heat curing, rough surface formation is conducted by an alkaline oxidant, and then, a conductor layer is formed on the surface by plating. In these cases, the method of making uneven or rough the surface of the insulating layer for the purpose of ensuring a satisfactory bonding strength between the conductor layer and the resin insulating layer is performed by a wet treatment, according to which a resin layer containing a component which can be decomposed by, or dissolved in, a rough surface-forming agent, such as an oxidant including potassium permanganate or the like, an alkali, or an organic solvent, is contacted with a rough surface-forming liquid (i.e., rough surface-forming agent or surface-roughening agent) by a wet treatment, such as immersion, spraying or the like.
Here, an ordinary conventional production method of a multilayer printed-wring board will be briefly explained.
First, as shown in FIG. 2(A), on the surface of insulating core material 1 made of, for example, a glass epoxy resin or the like, a predetermined wiring pattern 2 is formed with the use of copper foil or the like, and onto the entire surface of this core material 1, an insulating layer 3 is application-formed by a method such as screen printing or the like. The major material of the materials for this insulating layer 3 is composed of an epoxy resin, and in the resin of this insulating layer 3, filler 4 is mixed in an appropriate amount to be dissolved in the below-deseribed rough surface formation step.
Next, as shown in FIG. 2(B), holes for connection 6 are selectively formed at predetermined positions using, for example, a carbon dioxide gas laser 5 so that the holes penetrates the above-mentioned insulating layer 3, whereby the internal wiring pattern 2 is exposed, 7 indicating the roughened surface of the wiring pattern. Then, as shown in FIG. 2(C), the surface of the above-mentioned insulating layer 3 is affected with an alkaline rough surface-forming chemical liquid, for example, potassium permanganate or the like, so that the above-mentioned filler 4 which is soluble in the above rough surface-forming chemical liquid is dissolved whereby a number of uneven portions 8 are formed, thus effecting the rough surface formation on the insulating layer 3.
Then, by performing electroless plating and subsequently electroplating, as shown in FIG. 2(D), a conductor layer for electroplating 10 composed of, for example, copper or the like and a conductor layer 11 are subsequently formed. Thus, conduction between the conductor layer 11 and the wring pattern 2 which is the ground work can be made. Further, this conductor layer 11 is subjected to etching to obtain a second layer wring pattern 12.
In an ordinary process, subsequently, another insulating layer is formed, followed by conducting another wiring-patterning, and the above-mentioned steps are repeated, to thereby produce a multilayer printed-wiring board.
By the way, in this type of a wet treatment, it is necessary to perform a satisfactory bath control, with respect to the ion concentration and the pH of the rough surface-forming liquid, the bath temperature and the like, and hence, not only is the operation very cumbersome, but also there has been a problem about the waste liquid due to the life of bath.
Further, with the line width and the width between the lines being reduced, filler 4 having a still smaller particle diameter is demanded; however, the filler 4 can only be reduced in particle diameter to about 10 xcexcm at the smallest, and if one or five minutes of processing is performed in such a state, a problem also arises that the bonding strength between the insulating layer and the conductor layer is lowered.
Furthermore, even if it is possible to obtain a filler 4 having a still smaller particle diameter, there is also a problem that in the electroless plating conducted in a subsequent-step, the treatment liquid is difficult to enter.
Problems to be Solved by the Invention
The present invention has been made for solving the above-mentioned problems effectively, and it is an object to provide an insulating resin composition for a multilayer printed-wiring board, which can ensure the bonding strength of a conductor layer with an insulating layer by performing a rough surface formation by a dry treatment, such as plasma or sputtering or the like, without performing a wet treatment which has conventionally been conducted for the rough surface formation, and can satisfy heat resistance and electrically insulating properties.
Means to Solve the Problems
The present inventors have conducted made extensive and intensive studies with a view to solving the above-mentioned problems. As a result, it has been found that the below-described resin composition has extremely excellent performance, on the basis of which the present invention has been completed.
Specifically, the present invention relates to an insulating resin composition for a multilayer printed-wiring board which composition is to be used to form, or as, an insulating layer of the multilayer printed-wiring board, wherein for obtaining a roughness or unevenness by plasma treatment on the surface of the, insulating layer resulting from the insulating resin composition, the said insulating resin composition comprises two or more kinds of resins which are different in etching rate by a plasma treatment and which are not compatible with each other.
Thus, it has become possible to perform fine roughness formation treatment on the surface of the insulating layer by a dry treatment, such as a plasma treatment or the like. In this case, it is preferred that a surface roughness degree of the above-mentioned insulating layer by the plasma treatment is adjusted so as to be in the range of 100 to 4,000 nm.